1. Field of the Invention
The present invention relates to a fuel reformer for reforming fuel, and particularly to a fuel reformer which reforms and activates fuel supplied to a combustion chamber of an apparatus or equipment for obtaining power, heat generation, etc. by combustion of fuel such as a boiler, a heat treat furnace, a heating furnace, an internal combustion engine, a space heater, a drier and others (they are generally called as “combustion apparatus” in this specification).
2. Description of Related Art
Various measures for improvement of air pollution have been taken recently for preservation of global environment, and taking the auto industry as an example, various measures to reduce emissions have been promoted.
Particularly, in the case of a diesel-engine vehicle, its emission contains NOx which is said to cause health hazards such as respiratory disorders, bronchitis, lung cancer, etc. as well as particulate materials (PM) causing black smoke and hazardous materials such as carbon dioxide causing global warming. Among them, the PM causes not only asthma but its carcinogenicity has been pointed out recently. It is very important to reduce emission of PM in addition to reduction of NOx as a measure against air pollution.
Therefore, in the emission material control for a diesel vehicle in large cities by a government, PM was included in addition to NOx which is the conventional target materials for regulation, and for the type of vehicle, a diesel standard-sized car was also included in addition to large-sized cars such as trucks and buses. And the necessity to reduce emission of these hazardous materials has been increased.
To be concrete, in order to meet the criteria of the regulation for a diesel vehicle passing through a large city in the future, it will be necessary to replace a vehicle with one provided with a new diesel engine or to attach an apparatus for reducing the emission of the hazardous materials.
In order to cope with such a situation, various apparatuses have been developed for reducing the hazardous materials in the emission of an automobile. For example, there is known as an emission purifying apparatus a “diesel particulate filter (hereinafter referred to as “DPF”) placed in the middle of an exhaust passage for the emission for absorbing and removing PM exhausted by a diesel engine.
This DPF consists of a collection of porous ceramic cells in the honeycomb structure for capturing PM exhausted from the diesel engine when it passes through the wall of the cell and burning it so that diffusion of PM into the air is restrained.
However, DPF has the following problems.
Though the DPF can effectively reduce PM, it can not reduce both PM and NOx since a technology to remove NOx at the same time has not been established.
A catalyst capable of reducing both PM and NOx has been developed, but it is indispensable for the catalyst to use an engine provided with a common rail (electronic controlled fuel injection device). And moreover, diesel oil with high sulfur level can not be used due to the sulfur which makes lowering of purifying capability unavoidable, and the life depends on the quality of the diesel oil, which constitutes a problem.
Also, it is necessary to develop the DPF in combination with the engine control technology to securely burn the PM and to reduce the emission. Therefore, the DPF to be attached to new cars should be developed jointly with diesel engine manufacturers. And the DPF for post-attachment should be designed for each model, and since an engine is a core part of an automobile and is therefore developed for each affiliation, transaction outside the affiliation is difficult, compatibility is poor and after-sale service has a problem.
In the meantime, an emission purifying apparatus with the purpose of removing NOx contained in the emission is disclosed such as those using NOx reduction catalyst for reducing and dissolving NOx. But there is a problem that a high temperature is needed to activate the catalyst or the necessity to add fuel in the emission as a reducing agent complicates the constitution of the device.
The methods for removing the hazardous materials reduce the emission of the hazardous materials emitted into the air by removing the hazardous materials in the emission and then exhausting them, but if the fuel consumption itself required for obtaining the same workload can be decreased, the emission of the hazardous materials can be relatively reduced.
In this way, such a method with the purpose of improving fuel efficiency by activating fuel to be supplied to a combustion apparatus, more particularly, an internal combustion engine, is proposed in the Japanese Unexamined Patent Publication No. 10-196496 that a catalyst in which a precious metal is adsorbed to a porous ceramic is made and this is inputted and immersed in fuel liquid, or a paint in which a catalyst powder is diffused is applied in a tank so as to improve combustion efficiency with that catalyst.
Also, a fuel reformer for carrying out the fuel activation using a photocatalyst is proposed (Japanese Unexamined Patent Publications Nos. 10-176615, 10-265783 and 2004-52601).
Among the prior arts, the method in Japanese Unexamined Patent Publication No. 10-196496 describes that “NOx or SOx can not be removed safely as long as air is burned” through the fuel activation (Lines 29 to 31 on the Left column in Page 6). In order to remove NOx or others, it is necessary to add an additive to the fuel itself or to add a device to clean the emission with a special cleaning liquid in the exhaust system, which makes the apparatus itself large. And it also has various practical problems such as the necessity of drastic reform of the fuel supply and exhaust systems in the internal combustion engine.
In addition, a fuel reservoir tank using a photocatalyst as a fuel reformer catalyst is proposed in Japanese Unexamined Patent Publication No. 10-176615, but this photocatalyst exerts photocatalytic effect in response to the ultraviolet ray. Thus, in order to obtain the photocatalytic effect in the reservoir tank into which the ultraviolet ray does not reach, it is necessary to provide a light source for irradiating the photocatalyst with the ultraviolet, which makes the constitution of the device complicated and large. Therefore, the fuel reservoir tank in Japanese Unexamined Patent Publication No. 10-176615 becomes a relatively large apparatus, which causes a problem to restrict its installation location such that it can not be mounted on a vehicle.
Also, a fuel reformer which can be mounted on a vehicle and uses a photocatalyst supported by a porous material of a pellet-state particle as a fuel reforming catalyst is disclosed (Japanese Unexamined Patent Publication No. 10-265783), but the photocatalyst used in this apparatus also needs ultraviolet irradiation, and it is necessary to provide a special light source for irradiating ultraviolet rays when installed in a fuel supply system of an automobile into which the ultraviolet rays do not reach, and also, regular maintenance is required for the light source. Moreover, when the porous materials are contained closely in a sealed container of the fuel reformer apparatus, the ultraviolet irradiated from the light source is blocked by other porous materials and does not reach the porous materials with a distance from the light source, and the photocatalytic effect can not be fully exerted.
On the other hand, when the number of porous materials contained in the sealed container is decreased to enable full irradiation of the ultraviolet rays, the fuel reforming performance is lowered and problems can happen that the porous materials collide with each other and crush due to vibration when the automobile is driving or that broken pieces generated by the crush clog the fuel filter.
In the meantime, in the fuel reformer in the Japanese Unexamined Patent Publication No. 2004-52601, a porous plate made of lath-state mesh or honeycomb structure on the surface of which a layer of a photocatalytic material is formed is arranged in a chamber of a casing through which the fuel passes, and the layer of the photocatalytic material formed on this porous plate is brought into contact with the fuel for reforming the fuel. The photocatalytic material for reforming the fuel is a metal oxide layer having a structure which exerts the photocatalytic performance in response even to electromagnetic waves (gamma ray, X-ray, visible ray, infrared ray and electromagnetic wave) with the wavelength longer than that of the ultraviolet ray and a bond with oxygen is gradually decreased as goes from the surface to the inside (called as “oxygen deficit tilting structure” in this specification), and even if the fuel reformer is made by containing it in a casing through which the ultraviolet ray does not pass and a light source for irradiating the ultraviolet ray is not provided in the casing, fuel reform can be performed.
However, in the fuel reformer in this publication, the porous plate on the surface of which a layer of metal oxide having the oxygen deficit tilting structure is formed as a catalytic material contained in the casing is included, but the fuel reforming efficiency has hit a peak in the fuel reformer with such a structure, and a fuel reformer with higher efficiency can not be realized.
As an example, in the fuel reformer described as a Test Example 1 in the above Publication, “600 pieces of titanium lath” were used instead of “38 pieces of titanium lath+18 pieces of ceramic honeycombs” used as the porous plate, which is the catalytic material, and the fuel consumption rate was measured with the other conditions made common, but despite the increase in the surface area of the porous plate of about 10 times, improvement of the fuel consumption rate more than the fuel consumption rate described in the Example 1 of the Publication could not be achieved.
The above purpose such as improvement of fuel cost or prevention of generation of hazardous materials is not a problem specific to an internal combustion engine such as the diesel engine but is a common problem for various combustion apparatuses for obtaining generation of power or heat by burning fuel.
Thus, the present invention has an object to provide a fuel reformer which can reform fuel with higher efficiency, supplied to the combustion apparatuses obtaining power or heat by burning fuel such as a boiler, a heat treat furnace, a heating furnace, an internal combustion engine, a space heater, a drier and others, while keeping the advantageous characteristics in the fuel reformer in Japanese Unexamined Patent Publication No. 2004-52601 that provision of a light source or the like for irradiating the ultraviolet ray is not needed and the constitution is relatively simple, light-weight and small-sized so that a target for application is not limited, and it is also an object of the present invention to provide a fuel reformer which can relatively reduce emissions of nitrogen oxide (NOx), particulate material (PM), carbon dioxide, etc. generated with operation of a combustion apparatus by further improving the fuel consumption rate of these combustion apparatuses so as to reduce the fuel quantity to be used.